X-Git-Url: https://git.camperquake.de/gitweb.cgi?a=blobdiff_plain;f=module%2Fzfs%2Ftxg.c;h=7c820af4f8b3e8f6f6b070c2d2bba6745d015e4d;hb=refs%2Fheads%2Frertzinger%2Ffeature-zpool-get--p;hp=e3c0e2a134239eb05cd9f4c98c0574f49dfcc670;hpb=fb5f0bc83330c8a0236c4d34a23723ac1974971a;p=zfs.git diff --git a/module/zfs/txg.c b/module/zfs/txg.c index e3c0e2a..7c820af 100644 --- a/module/zfs/txg.c +++ b/module/zfs/txg.c @@ -19,24 +19,97 @@ * CDDL HEADER END */ /* - * Copyright 2008 Sun Microsystems, Inc. All rights reserved. - * Use is subject to license terms. + * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. + * Portions Copyright 2011 Martin Matuska + * Copyright (c) 2013 by Delphix. All rights reserved. */ #include #include #include +#include #include +#include #include +#include /* - * Pool-wide transaction groups. + * ZFS Transaction Groups + * ---------------------- + * + * ZFS transaction groups are, as the name implies, groups of transactions + * that act on persistent state. ZFS asserts consistency at the granularity of + * these transaction groups. Each successive transaction group (txg) is + * assigned a 64-bit consecutive identifier. There are three active + * transaction group states: open, quiescing, or syncing. At any given time, + * there may be an active txg associated with each state; each active txg may + * either be processing, or blocked waiting to enter the next state. There may + * be up to three active txgs, and there is always a txg in the open state + * (though it may be blocked waiting to enter the quiescing state). In broad + * strokes, transactions — operations that change in-memory structures — are + * accepted into the txg in the open state, and are completed while the txg is + * in the open or quiescing states. The accumulated changes are written to + * disk in the syncing state. + * + * Open + * + * When a new txg becomes active, it first enters the open state. New + * transactions — updates to in-memory structures — are assigned to the + * currently open txg. There is always a txg in the open state so that ZFS can + * accept new changes (though the txg may refuse new changes if it has hit + * some limit). ZFS advances the open txg to the next state for a variety of + * reasons such as it hitting a time or size threshold, or the execution of an + * administrative action that must be completed in the syncing state. + * + * Quiescing + * + * After a txg exits the open state, it enters the quiescing state. The + * quiescing state is intended to provide a buffer between accepting new + * transactions in the open state and writing them out to stable storage in + * the syncing state. While quiescing, transactions can continue their + * operation without delaying either of the other states. Typically, a txg is + * in the quiescing state very briefly since the operations are bounded by + * software latencies rather than, say, slower I/O latencies. After all + * transactions complete, the txg is ready to enter the next state. + * + * Syncing + * + * In the syncing state, the in-memory state built up during the open and (to + * a lesser degree) the quiescing states is written to stable storage. The + * process of writing out modified data can, in turn modify more data. For + * example when we write new blocks, we need to allocate space for them; those + * allocations modify metadata (space maps)... which themselves must be + * written to stable storage. During the sync state, ZFS iterates, writing out + * data until it converges and all in-memory changes have been written out. + * The first such pass is the largest as it encompasses all the modified user + * data (as opposed to filesystem metadata). Subsequent passes typically have + * far less data to write as they consist exclusively of filesystem metadata. + * + * To ensure convergence, after a certain number of passes ZFS begins + * overwriting locations on stable storage that had been allocated earlier in + * the syncing state (and subsequently freed). ZFS usually allocates new + * blocks to optimize for large, continuous, writes. For the syncing state to + * converge however it must complete a pass where no new blocks are allocated + * since each allocation requires a modification of persistent metadata. + * Further, to hasten convergence, after a prescribed number of passes, ZFS + * also defers frees, and stops compressing. + * + * In addition to writing out user data, we must also execute synctasks during + * the syncing context. A synctask is the mechanism by which some + * administrative activities work such as creating and destroying snapshots or + * datasets. Note that when a synctask is initiated it enters the open txg, + * and ZFS then pushes that txg as quickly as possible to completion of the + * syncing state in order to reduce the latency of the administrative + * activity. To complete the syncing state, ZFS writes out a new uberblock, + * the root of the tree of blocks that comprise all state stored on the ZFS + * pool. Finally, if there is a quiesced txg waiting, we signal that it can + * now transition to the syncing state. */ static void txg_sync_thread(dsl_pool_t *dp); static void txg_quiesce_thread(dsl_pool_t *dp); -int zfs_txg_timeout = 30; /* max seconds worth of delta per txg */ +int zfs_txg_timeout = 5; /* max seconds worth of delta per txg */ /* * Prepare the txg subsystem. @@ -48,7 +121,7 @@ txg_init(dsl_pool_t *dp, uint64_t txg) int c; bzero(tx, sizeof (tx_state_t)); - tx->tx_cpu = kmem_zalloc(max_ncpus * sizeof (tx_cpu_t), KM_SLEEP); + tx->tx_cpu = vmem_zalloc(max_ncpus * sizeof (tx_cpu_t), KM_SLEEP); for (c = 0; c < max_ncpus; c++) { int i; @@ -57,10 +130,12 @@ txg_init(dsl_pool_t *dp, uint64_t txg) for (i = 0; i < TXG_SIZE; i++) { cv_init(&tx->tx_cpu[c].tc_cv[i], NULL, CV_DEFAULT, NULL); + list_create(&tx->tx_cpu[c].tc_callbacks[i], + sizeof (dmu_tx_callback_t), + offsetof(dmu_tx_callback_t, dcb_node)); } } - rw_init(&tx->tx_suspend, NULL, RW_DEFAULT, NULL); mutex_init(&tx->tx_sync_lock, NULL, MUTEX_DEFAULT, NULL); cv_init(&tx->tx_sync_more_cv, NULL, CV_DEFAULT, NULL); @@ -83,7 +158,6 @@ txg_fini(dsl_pool_t *dp) ASSERT(tx->tx_threads == 0); - rw_destroy(&tx->tx_suspend); mutex_destroy(&tx->tx_sync_lock); cv_destroy(&tx->tx_sync_more_cv); @@ -96,11 +170,16 @@ txg_fini(dsl_pool_t *dp) int i; mutex_destroy(&tx->tx_cpu[c].tc_lock); - for (i = 0; i < TXG_SIZE; i++) + for (i = 0; i < TXG_SIZE; i++) { cv_destroy(&tx->tx_cpu[c].tc_cv[i]); + list_destroy(&tx->tx_cpu[c].tc_callbacks[i]); + } } - kmem_free(tx->tx_cpu, max_ncpus * sizeof (tx_cpu_t)); + if (tx->tx_commit_cb_taskq != NULL) + taskq_destroy(tx->tx_commit_cb_taskq); + + vmem_free(tx->tx_cpu, max_ncpus * sizeof (tx_cpu_t)); bzero(tx, sizeof (tx_state_t)); } @@ -129,7 +208,7 @@ txg_sync_start(dsl_pool_t *dp) * 32-bit x86. This is due in part to nested pools and * scrub_visitbp() recursion. */ - tx->tx_sync_thread = thread_create(NULL, 12<<10, txg_sync_thread, + tx->tx_sync_thread = thread_create(NULL, 32<<10, txg_sync_thread, dp, 0, &p0, TS_RUN, minclsyspri); mutex_exit(&tx->tx_sync_lock); @@ -159,9 +238,10 @@ txg_thread_wait(tx_state_t *tx, callb_cpr_t *cpr, kcondvar_t *cv, uint64_t time) CALLB_CPR_SAFE_BEGIN(cpr); if (time) - (void) cv_timedwait(cv, &tx->tx_sync_lock, lbolt + time); + (void) cv_timedwait_interruptible(cv, &tx->tx_sync_lock, + ddi_get_lbolt() + time); else - cv_wait(cv, &tx->tx_sync_lock); + cv_wait_interruptible(cv, &tx->tx_sync_lock); CALLB_CPR_SAFE_END(cpr, &tx->tx_sync_lock); } @@ -179,7 +259,11 @@ txg_sync_stop(dsl_pool_t *dp) * Finish off any work in progress. */ ASSERT(tx->tx_threads == 2); - txg_wait_synced(dp, 0); + + /* + * We need to ensure that we've vacated the deferred space_maps. + */ + txg_wait_synced(dp, tx->tx_open_txg + TXG_DEFER_SIZE); /* * Wake all sync threads and wait for them to die. @@ -206,9 +290,19 @@ uint64_t txg_hold_open(dsl_pool_t *dp, txg_handle_t *th) { tx_state_t *tx = &dp->dp_tx; - tx_cpu_t *tc = &tx->tx_cpu[CPU_SEQID]; + tx_cpu_t *tc; uint64_t txg; + /* + * It appears the processor id is simply used as a "random" + * number to index into the array, and there isn't any other + * significance to the chosen tx_cpu. Because.. Why not use + * the current cpu to index into the array? + */ + kpreempt_disable(); + tc = &tx->tx_cpu[CPU_SEQID]; + kpreempt_enable(); + mutex_enter(&tc->tc_lock); txg = tx->tx_open_txg; @@ -229,6 +323,17 @@ txg_rele_to_quiesce(txg_handle_t *th) } void +txg_register_callbacks(txg_handle_t *th, list_t *tx_callbacks) +{ + tx_cpu_t *tc = th->th_cpu; + int g = th->th_txg & TXG_MASK; + + mutex_enter(&tc->tc_lock); + list_move_tail(&tc->tc_callbacks[g], tx_callbacks); + mutex_exit(&tc->tc_lock); +} + +void txg_rele_to_sync(txg_handle_t *th) { tx_cpu_t *tc = th->th_cpu; @@ -246,6 +351,8 @@ txg_rele_to_sync(txg_handle_t *th) static void txg_quiesce(dsl_pool_t *dp, uint64_t txg) { + hrtime_t start; + txg_history_t *th; tx_state_t *tx = &dp->dp_tx; int g = txg & TXG_MASK; int c; @@ -267,8 +374,19 @@ txg_quiesce(dsl_pool_t *dp, uint64_t txg) mutex_exit(&tx->tx_cpu[c].tc_lock); /* + * Measure how long the txg was open and replace the kstat. + */ + th = dsl_pool_txg_history_get(dp, txg); + th->th_kstat.open_time = gethrtime() - th->th_kstat.birth; + th->th_kstat.state = TXG_STATE_QUIESCING; + dsl_pool_txg_history_put(th); + dsl_pool_txg_history_add(dp, tx->tx_open_txg); + + /* * Quiesce the transaction group by waiting for everyone to txg_exit(). */ + start = gethrtime(); + for (c = 0; c < max_ncpus; c++) { tx_cpu_t *tc = &tx->tx_cpu[c]; mutex_enter(&tc->tc_lock); @@ -276,37 +394,120 @@ txg_quiesce(dsl_pool_t *dp, uint64_t txg) cv_wait(&tc->tc_cv[g], &tc->tc_lock); mutex_exit(&tc->tc_lock); } + + /* + * Measure how long the txg took to quiesce. + */ + th = dsl_pool_txg_history_get(dp, txg); + th->th_kstat.quiesce_time = gethrtime() - start; + dsl_pool_txg_history_put(th); +} + +static void +txg_do_callbacks(list_t *cb_list) +{ + dmu_tx_do_callbacks(cb_list, 0); + + list_destroy(cb_list); + + kmem_free(cb_list, sizeof (list_t)); +} + +/* + * Dispatch the commit callbacks registered on this txg to worker threads. + */ +static void +txg_dispatch_callbacks(dsl_pool_t *dp, uint64_t txg) +{ + int c; + tx_state_t *tx = &dp->dp_tx; + list_t *cb_list; + + for (c = 0; c < max_ncpus; c++) { + tx_cpu_t *tc = &tx->tx_cpu[c]; + /* No need to lock tx_cpu_t at this point */ + + int g = txg & TXG_MASK; + + if (list_is_empty(&tc->tc_callbacks[g])) + continue; + + if (tx->tx_commit_cb_taskq == NULL) { + /* + * Commit callback taskq hasn't been created yet. + */ + tx->tx_commit_cb_taskq = taskq_create("tx_commit_cb", + 100, minclsyspri, max_ncpus, INT_MAX, + TASKQ_THREADS_CPU_PCT | TASKQ_PREPOPULATE); + } + + cb_list = kmem_alloc(sizeof (list_t), KM_PUSHPAGE); + list_create(cb_list, sizeof (dmu_tx_callback_t), + offsetof(dmu_tx_callback_t, dcb_node)); + + list_move_tail(cb_list, &tc->tc_callbacks[g]); + + (void) taskq_dispatch(tx->tx_commit_cb_taskq, (task_func_t *) + txg_do_callbacks, cb_list, TQ_SLEEP); + } +} + +/* + * Wait for pending commit callbacks of already-synced transactions to finish + * processing. + * Calling this function from within a commit callback will deadlock. + */ +void +txg_wait_callbacks(dsl_pool_t *dp) +{ + tx_state_t *tx = &dp->dp_tx; + + if (tx->tx_commit_cb_taskq != NULL) + taskq_wait(tx->tx_commit_cb_taskq); } static void txg_sync_thread(dsl_pool_t *dp) { + spa_t *spa = dp->dp_spa; tx_state_t *tx = &dp->dp_tx; callb_cpr_t cpr; uint64_t start, delta; +#ifdef _KERNEL + /* + * Annotate this process with a flag that indicates that it is + * unsafe to use KM_SLEEP during memory allocations due to the + * potential for a deadlock. KM_PUSHPAGE should be used instead. + */ + current->flags |= PF_NOFS; +#endif /* _KERNEL */ + txg_thread_enter(tx, &cpr); start = delta = 0; for (;;) { - uint64_t timer, timeout = zfs_txg_timeout * hz; + hrtime_t hrstart; + txg_history_t *th; + uint64_t timer, timeout; uint64_t txg; + timeout = zfs_txg_timeout * hz; + /* - * We sync when we're scrubbing, there's someone waiting + * We sync when we're scanning, there's someone waiting * on us, or the quiesce thread has handed off a txg to * us, or we have reached our timeout. */ timer = (delta >= timeout ? 0 : timeout - delta); - while ((dp->dp_scrub_func == SCRUB_FUNC_NONE || - spa_shutting_down(dp->dp_spa)) && + while (!dsl_scan_active(dp->dp_scan) && !tx->tx_exiting && timer > 0 && tx->tx_synced_txg >= tx->tx_sync_txg_waiting && tx->tx_quiesced_txg == 0) { dprintf("waiting; tx_synced=%llu waiting=%llu dp=%p\n", tx->tx_synced_txg, tx->tx_sync_txg_waiting, dp); txg_thread_wait(tx, &cpr, &tx->tx_sync_more_cv, timer); - delta = lbolt - start; + delta = ddi_get_lbolt() - start; timer = (delta > timeout ? 0 : timeout - delta); } @@ -324,8 +525,6 @@ txg_sync_thread(dsl_pool_t *dp) if (tx->tx_exiting) txg_thread_exit(tx, &cpr, &tx->tx_sync_thread); - rw_enter(&tx->tx_suspend, RW_WRITER); - /* * Consume the quiesced txg which has been handed off to * us. This may cause the quiescing thread to now be @@ -335,22 +534,47 @@ txg_sync_thread(dsl_pool_t *dp) tx->tx_quiesced_txg = 0; tx->tx_syncing_txg = txg; cv_broadcast(&tx->tx_quiesce_more_cv); - rw_exit(&tx->tx_suspend); + + th = dsl_pool_txg_history_get(dp, txg); + th->th_kstat.state = TXG_STATE_SYNCING; + vdev_get_stats(spa->spa_root_vdev, &th->th_vs1); + dsl_pool_txg_history_put(th); dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n", txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting); mutex_exit(&tx->tx_sync_lock); - start = lbolt; - spa_sync(dp->dp_spa, txg); - delta = lbolt - start; + start = ddi_get_lbolt(); + hrstart = gethrtime(); + spa_sync(spa, txg); + delta = ddi_get_lbolt() - start; mutex_enter(&tx->tx_sync_lock); - rw_enter(&tx->tx_suspend, RW_WRITER); tx->tx_synced_txg = txg; tx->tx_syncing_txg = 0; - rw_exit(&tx->tx_suspend); cv_broadcast(&tx->tx_sync_done_cv); + + /* + * Dispatch commit callbacks to worker threads. + */ + txg_dispatch_callbacks(dp, txg); + + /* + * Measure the txg sync time determine the amount of I/O done. + */ + th = dsl_pool_txg_history_get(dp, txg); + vdev_get_stats(spa->spa_root_vdev, &th->th_vs2); + th->th_kstat.sync_time = gethrtime() - hrstart; + th->th_kstat.nread = th->th_vs2.vs_bytes[ZIO_TYPE_READ] - + th->th_vs1.vs_bytes[ZIO_TYPE_READ]; + th->th_kstat.nwritten = th->th_vs2.vs_bytes[ZIO_TYPE_WRITE] - + th->th_vs1.vs_bytes[ZIO_TYPE_WRITE]; + th->th_kstat.reads = th->th_vs2.vs_ops[ZIO_TYPE_READ] - + th->th_vs1.vs_ops[ZIO_TYPE_READ]; + th->th_kstat.writes = th->th_vs2.vs_ops[ZIO_TYPE_WRITE] - + th->th_vs1.vs_ops[ZIO_TYPE_WRITE]; + th->th_kstat.state = TXG_STATE_COMMITTED; + dsl_pool_txg_history_put(th); } } @@ -407,7 +631,7 @@ void txg_delay(dsl_pool_t *dp, uint64_t txg, int ticks) { tx_state_t *tx = &dp->dp_tx; - int timeout = lbolt + ticks; + clock_t timeout = ddi_get_lbolt() + ticks; /* don't delay if this txg could transition to quiesing immediately */ if (tx->tx_open_txg > txg || @@ -420,11 +644,13 @@ txg_delay(dsl_pool_t *dp, uint64_t txg, int ticks) return; } - while (lbolt < timeout && + while (ddi_get_lbolt() < timeout && tx->tx_syncing_txg < txg-1 && !txg_stalled(dp)) (void) cv_timedwait(&tx->tx_quiesce_more_cv, &tx->tx_sync_lock, timeout); + DMU_TX_STAT_BUMP(dmu_tx_delay); + mutex_exit(&tx->tx_sync_lock); } @@ -436,7 +662,7 @@ txg_wait_synced(dsl_pool_t *dp, uint64_t txg) mutex_enter(&tx->tx_sync_lock); ASSERT(tx->tx_threads == 2); if (txg == 0) - txg = tx->tx_open_txg; + txg = tx->tx_open_txg + TXG_DEFER_SIZE; if (tx->tx_sync_txg_waiting < txg) tx->tx_sync_txg_waiting = txg; dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n", @@ -487,21 +713,6 @@ txg_sync_waiting(dsl_pool_t *dp) tx->tx_quiesced_txg != 0); } -void -txg_suspend(dsl_pool_t *dp) -{ - tx_state_t *tx = &dp->dp_tx; - /* XXX some code paths suspend when they are already suspended! */ - rw_enter(&tx->tx_suspend, RW_READER); -} - -void -txg_resume(dsl_pool_t *dp) -{ - tx_state_t *tx = &dp->dp_tx; - rw_exit(&tx->tx_suspend); -} - /* * Per-txg object lists. */ @@ -529,7 +740,7 @@ txg_list_destroy(txg_list_t *tl) mutex_destroy(&tl->tl_lock); } -int +boolean_t txg_list_empty(txg_list_t *tl, uint64_t txg) { return (tl->tl_head[txg & TXG_MASK] == NULL); @@ -559,6 +770,34 @@ txg_list_add(txg_list_t *tl, void *p, uint64_t txg) } /* + * Add an entry to the end of the list (walks list to find end). + * Returns 0 if it's a new entry, 1 if it's already there. + */ +int +txg_list_add_tail(txg_list_t *tl, void *p, uint64_t txg) +{ + int t = txg & TXG_MASK; + txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset); + int already_on_list; + + mutex_enter(&tl->tl_lock); + already_on_list = tn->tn_member[t]; + if (!already_on_list) { + txg_node_t **tp; + + for (tp = &tl->tl_head[t]; *tp != NULL; tp = &(*tp)->tn_next[t]) + continue; + + tn->tn_member[t] = 1; + tn->tn_next[t] = NULL; + *tp = tn; + } + mutex_exit(&tl->tl_lock); + + return (already_on_list); +} + +/* * Remove the head of the list and return it. */ void * @@ -637,3 +876,23 @@ txg_list_next(txg_list_t *tl, void *p, uint64_t txg) return (tn == NULL ? NULL : (char *)tn - tl->tl_offset); } + +#if defined(_KERNEL) && defined(HAVE_SPL) +EXPORT_SYMBOL(txg_init); +EXPORT_SYMBOL(txg_fini); +EXPORT_SYMBOL(txg_sync_start); +EXPORT_SYMBOL(txg_sync_stop); +EXPORT_SYMBOL(txg_hold_open); +EXPORT_SYMBOL(txg_rele_to_quiesce); +EXPORT_SYMBOL(txg_rele_to_sync); +EXPORT_SYMBOL(txg_register_callbacks); +EXPORT_SYMBOL(txg_delay); +EXPORT_SYMBOL(txg_wait_synced); +EXPORT_SYMBOL(txg_wait_open); +EXPORT_SYMBOL(txg_wait_callbacks); +EXPORT_SYMBOL(txg_stalled); +EXPORT_SYMBOL(txg_sync_waiting); + +module_param(zfs_txg_timeout, int, 0644); +MODULE_PARM_DESC(zfs_txg_timeout, "Max seconds worth of delta per txg"); +#endif